Soil microbes are ubiquitous, diverse and impact global nutrient cycling and biogeochemical structuring, yet much of our current understanding is built largely on what is known about culturable ebacteria, which comprise < 1% of the total microbial diversity. Advances in culturing methods and culture-independent approaches are essential to gain a more complete understanding of the microbial world. Our laboratories have developed metagenomics, which is a culture-independent approach to identifying genes and activities from soil microbes, thereby broadening our understanding of the uncultured microbes. Functional metagenomics relies on heterologous expression of foreign genes in Escherichia coli and other host species, and therefore the role of transcriptional factors in heterologous expression is integral to metagenomic analysis. My overall hypothesis is that introduction and manipulation of sigma factors can expand the range of genes from cultured and uncultured bacteria expressed in E. coli. My sub-hypotheses to be tested are: 1) Acidobacterium capsulatum RpoD will increase expression of Acidobacterium genes in E. coli 2) Induction of E. coli heat shock sigma factor (RpoH) will increase the likelihood of identifying tellurite resistance genes from Rhodobacter sphaeroides and uncultured bacteria The goal of this research is to establish the influence of sigma factors on heterologous gene expression. My research will contribute to our understanding of sigma factors and gene regulation and resulting in a novel functional characterization of genes from cultured and uncultured bacteria.